I’ve found WaniKani to be amazing for SRS for kanji. If you are diligent about it you can go through the jouyou set in 18 months or so.
The nice thing about Duolingo for, say, French is that I can kind of mindlessly do it every day to keep my skills up and improve my vocabulary, and then do smaller bouts of studying using other methods to improve actual fluency.
But with Japanese, Duolingo just doesn't work very well, and just learning kanji with WaniKani would miss all of the rest of the context, so I'd need something to pair with that for learning the rest of the language. Any recommendations on good resources for learning the actual spoken language to go along with WaniKai?
BunPro is pretty good. It's fairly light on its own lessons, but will point in the right direction for material on each grammar point (both online and in the Genki books), and then has a spaced repetition framework for practice/memorising. It also ties into WaniKani fairly well, so that once you've learnt a kanji in WaniKani it will stop showing the furigana so you get kanji practice at the same time.
There's a WK deck if you really want to use their content.